FR2867316A1 - Insulating flexible tube, useful for receiving electric cables, comprises main tubular wall insulated by a thermo plastic material and an insulating external wall made up of another immiscible thermoplastic material - Google Patents

Abstract

Insulating flexible tube (I) (preferably passage cables for electric installations) comprises a main tubular wall (2) insulated by a thermoplastic material and an insulating external wall (3) made up of another immiscible thermoplastic material, which covers the main insulating wall having concordant sensitive waves with corresponding waves of the main insulating wall. Independent claims are also included for: (1) the preparation of (I); and (2) an instrument for preparing (I) comprising a main extrude for the extrusion of the thermoplastic material; a head for extrusion, which drags the distribution of the flow of the second material on the first material avoiding the formation of a mixture, bound to the main extrude and to the co-extrude, equipped at the first opening for the flow from the first extrude material to the semi-fluid state and from a second opening for the flow of the second material such that it covers externally the flow of the first material; a pair of tubular passage of co axial outlets bound to the head of the extrusion to give, the flow of the first recovered material by the second material, a sensitive tubular flow to obtain a tube with double coating wall; a device for insulation associated with the outlet passage and comprising some profiled moulds to insulate the tube with double coating; and another tubular passage for the introduction of a fluid for blowing inside the tube with a wall of double coating in a manner to stretch and adhere to the profiled moulds and produce double coated insulating wall.

Description

FLEXIBLE PIPE OF PREFERENCE TYPE PASSING OF

  CABLES AND METHOD OF MANUFACTURING THE SAME

  The present invention relates to a corrugated flexible tube, preferably of the type of cable passage for electrical installations.

  Currently, the flexible cable ducts for electrical wiring increasingly used in the context of facilities, as they facilitate the laying of electrical cables passing through gaps provided in the walls or below the floor of homes or offices. In addition, the use of the cable passage tubes ensures a significant protection of these cables against external effects such as, for example, crushing or corrosive actions that can damage them by reducing their exercise period.

  Flexible cable ducts are known to be manufactured using one. thermoplastic material such as, for example, polyvinyl chloride (PVC), polyethylene or polypropylene. Such materials combine good properties of resistance to internal pressure and external stresses with considerable lightness.

  One particular type of flexible cable duct is constituted by the corrugated tubes. As is known to those skilled in the art, the traditional corrugated flexible cable ducting tubes (made of PVC or other thermoplastic material) are constituted by a corrugated wall, that is to say shaped so as to include a regular succession of annular-shaped projections which follow one another in a longitudinal direction of the tube. Each projection is separated from the next by a corresponding valley.

  In the context of the present invention, it is understood by corrugated tube a tube which has the succession of projections and undulations due to the undulation both externally and internally. Generally, the succession of projections and undulations present inside is offset from that outside.

  Advantageously, the corrugation of the cable passage tubes confers them to the. times greater crush strength and greater flexibility that makes them flexible and adaptable to the interstices in which they must be housed.

  As is known, conventional corrugated flexible cable ducting tubes are manufactured by extruding PVC from a profiled opening of a perforated plate or die placed at the exit of a machine for extrusion. The extruded PVC is sent to a ripple device. This device is provided with profiled corrugated molds so as to reproduce the shapes of the corrugation. When the extruded PVC is in correspondence of the corrugation molds, the thermoplastic material is expanded by means of a suitable air blowing so that it adheres to the molds. Simultaneously, the molds of the corrugator condense the PVC by solidifying it in the final corrugated tubular form.

  A disadvantage of conventional flexible corrugated tubes for the passage of cables is related to the presence of discontinuities or micropores in the wall of the tube. It has been perceived that these micropores are generated as a result of the blowing operation necessary for the waving. In particular, it has been observed that micropores should be attributed to the presence of impurities or micrograins present within the extruded material.

  The aforementioned discontinuities are accentuated by the effect of the expansion and stretching of the PVC following the blowing and can cause microscopic undulations or true through holes in the wall of the cable ducts, in particular in the case of walls. thin.

  It is observed that the presence of the micropores in the walls of the corrugated flexible cable duct tube can prevent the easy and rapid passage of electrical cables inside the tube during the implementation of the facilities. Indeed, a liquid construction material (for example, concrete) which is poured on the corrugated tube of cable passage would succeed in passing inside the tube through the holes present therein. Successively, once cured, the concrete would prevent the passage of electrical cables inside the corrugated pipe, with a consequent loss of all the benefits described above.

  The purpose of the present invention is a corrugated flexible cable duct tube that overcomes the disadvantages of traditional corrugated flexible tubes while being at the same time economical to achieve.

  A method of manufacturing the corrugated tube and apparatus used in said method also form an object of the present invention.

  The features and advantages of the present invention will emerge from the following detailed description of an exemplary embodiment and in no way limiting with reference to the accompanying drawings, in which: FIG. perspective of an example of corrugated flexible tube according to the present invention; Figs. 2A and 2B show respectively a side view and a cross-sectional view of the corrugated flexible tube of Fig. 1; Figure 3 is a portion of a longitudinal section of the tube of Figure 1 which shows the structure of a wall of the tube; Figure 4 shows an apparatus for manufacturing the corrugated tube of Figure 1; Figures 5A and 5B show perforated plates usable in the apparatus of Figure 4; FIGS. 6A, 6B and 6C show in sequence the phases of a corrugation procedure of the tube of FIG. 1.

  Referring to Figures 1, 2A, 2B and 3 will now be described an embodiment of a corrugated flexible tube cable passage 1 according to the invention. This tube 1 comprises a corrugated wall 4, that is to say shaped so as to have an alternation of projections 5 and undulations 6 which follow one another along the longitudinal axis of the tube 1.

  In particular, this wall 4 comprises two superimposed walls and precisely a corrugated inner main tubular wall 2 and a corrugated outer tubular wall 3 which covers the main wall 2. In particular, the outer wall 3 has corrugations substantially matching those of the wall main 2, that is to say that the outer wall 3 adheres.

  to the main wall 2 having a protective sheath function for the latter.

  The main wall 2 is made of a first thermoplastic material, while the outer wall 3 is made of a second thermoplastic material different from the first thermoplastic material. It is observed that an example of a method of manufacturing the corrugated flexible tube by means of a coextrusion procedure will be described in more detail below.

  Advantageously, the first and second thermoplastic materials have the characteristic of not being miscible with each other, that is to say they are such that when they are. contacted in the molten or half-melted state during coextrusion, they do not form a solution.

  For example, the thermoplastic material of the main parci 2 is polyvinyl chloride (PVC), while that of the outer wall 3 is polypropylene or polyethylene, or vice versa.

  In a preferred embodiment, the flexible cable passage tube 1 has, for example, an outer diameter of 20 mm and an inner diameter of 14 mm. In addition, the total weight of this double-walled tube is, for example, 68 grams per meter.

  Preferably, the main wall 2 has a thickness and a weight per meter greater than that of the outer wall 3. In more detail, the main wall 2 made of PVC has, for example, a weight of 52 grams per meter, while the outer wall 3 polypropylene weighs, for example, 16 grams per meter.

  It is observed that at equal thickness of the thermoplastic materials used, the thicknesses of the main and outer walls 3 and 3 can be modified to ensure adequate resistance of the tube to crushing.

  Apparatus 100 for manufacturing the corrugated flexible tube of FIG. 1 is shown schematically in FIG.

  In particular, this apparatus 100 comprises a main extruder (or drawing machine) 7 and a secondary extruder or co-extruder 8 for separately treating the first and second thermoplastic material, used in the manufacture of the walls of the tube. Each extruder comprises a hopper 9 for introducing the thermoplastic material into a body 10 of the main extruder 7 and the co-extruder 8. This body 10 may have, for example, a parallelepipedal or cylindrical shape and comprises inside the compression and thrust means (not shown in Figure 4) such as, for example, a screw for compressing, melting and homogenizing the aforementioned thermoplastic material.

  Advantageously, the main extruder 7 and the coextruder 8 share the same outlet portion or extrusion head 11. In particular, according to the diagram of FIG. 4, a first tubular connecting duct 12 connects the main extruder 7 longitudinally to a first inlet end 16 of the extrusion head 11. Similarly, a second tubular connecting pipe 13 connects the coextruder 8 transversely to a second inlet end 17 of the head 11. It is observed that , according to the example of Figure 4, the second duct 13 is tapered at the end near the second inlet 17 to provide the necessary flow of the second = thermoplastic material.

  The extrusion head 11 comprises a coextrusion section 11a located in correspondence of an outlet end 14 of the same head 11 and opposite to the aforementioned first inlet end 16.

  According to a particular embodiment, inside this coextrusion section lla are installed two perforated plates or metal dies (not visible in Figure 4) connected together in a suitable manner.

  For example, a perforated plate 22 in the coextrusion section 11a is shown in FIG. 5A. This plate 22 comprises a first opening 23 corresponding to an outlet mouth of the first connecting pipe 12 to allow the exit of the first thermoplastic material coming from the main extruder 7.

  In addition, the perforated plate 22 is provided with a second opening 24 which corresponds to a mouth c.e outlet of the second conduit 13 to allow the exit c.0 second thermoplastic material of the coextruder 8.

  This first opening 23 is located in correspondence of a recess or concave zone 28 of the plate 22, separated from the remaining planar surface 29 of the plate 22 by means of grooves 25, 26, 27 which gradually decrease towards this concave region. 28.

  In particular, the grooves 25, 26, 27 are profiled to promote sliding and uniform distribution of the second semi-fluid material on the first thermoplastic material present. at the level of the first opening 23.

  In the coextrusion section 11a is inserted another plate 22 ', shown in FIG. 5B, structurally similar to the plate 22. In FIG. 5B, the elements of the other plate 22' are similar to those of FIG. plate 22 are indicated by the same reference numerals followed by a prime sign '.

  This other plate 22 'comprises a corresponding concave zone 28', a corresponding first opening 23 'and corresponding grooves 25', 26 ', 27'.

  Unlike the plate 22, said other plate 22 'does not have any direct connection openings with the second tubular conduit 13.

  Advantageously, the flat surfaces 29 and 29 'of the plates 22 and 22' comprise holes H suitable for the passage of fixing elements (for example, bolts) for the mechanical coupling of the two plates.

  Inside the coextrusion section 11a, the two perforated plates 22, 22 'are presented to each other so that the grooves 25-27 and the first opening 23 are facing the grooves 25'. -27 'and the opening 23'. Advantageously, the concave zones 28 and 28 'of the two plates 22 and 22' determine a coextrusion chamber within which a half-melted flow of the second thermoplastic material can flow appropriately over a flow of the first material. .

  In addition, a first 18 and a second 19 tubular outlet ducts are connected to the output end 14 of the extrusion head 11. These outlet ducts are: the same longitudinal axis and are one to the inside each other. As is known to those skilled in the art, the first outlet duct 18 (internal) and the second outlet duct 19 (outer) coaxial therewith are generally called male and female. Between these conduits passes the extruded thermoplastic materials simultaneously to be fed to a corrugator device 15.

  It is observed that another tubular duct 21 is connected to the extrusion head 11. In more detail, this tubular duct 21 is connected to the first tubular outlet duct 18 inside the extrusion head 11 to favor introducing air (in the direction indicated by arrow F) into the outlet duct 18 during a ripple procedure which will be described later.

  It is observed that the corrugation device 15 shown diagrammatically in FIG. 4 comprises, in general, two profiled parts or molds 20 juxtaposed in rotation.

  These profiled parts 20, also called profiled shells, comprise a succession of projections and recesses to give the corrugated tube its outer shape.

  A method of manufacturing the corrugated cable duct tube of the invention will now be described with particular reference to FIGS. 6A, 6B and 6C.

  It is observed that in the description below, it will be assumed, by way of example, as first and second thermoplastic material PVC and polypropylene, respectively.

  Firstly, PVC and polypropylene, in the form of crumbled pellets, are introduced (through the hoppers 9) into the respective extruders, that is to say that the PVC is introduced into the main extruder 7 and the polypropylene inside the co-extruder 8.

  The pellets of thermoplastic material are compressed and heated to form a semi-fluid mass. For example, the PVC is heated to the temperature of 195 C while the polypropylene up to the temperature of 220 C.

  The masses thus obtained are homogenized and pushed to the extrusion head 11 through the first 12 and the second conduit 13.

  In correspondence with the coextrusion section 11a and, in particular, with the plate 22, the PVC semi-fluid mass is extruded into a substantially continuous and homogeneous flow through the first opening 23. Simultaneously, the semi-fluid mass of polypropylene, extruded through the second opening 24, discharges onto the PVC by uniformly distributing around said PVC continuous flow as a consequence of the geometry of the grooves 25-27, 25'-27 '(as shown schematically by the arrows of Figure 5A). Indeed, the latter are profiled so as to offer less resistance to the passage of the polypropylene so that it can be distributed uniformly in correspondence of all the passage sections.

  In addition, it is observed that the PVC and the polypropylene not being miscible with each other, even in the half-melted state, do not amalgamate, that is to say that they do not form a mixture or unique solution.

  In other words, PVC and polypropylene give rise to adherent but distinct walls.

  Then, the continuous and homogeneous stream of PV2 coated by the polypropylene layer leaves the extrusion head 11 to be fed to the corrugation device 15.

  This homogeneous flux coated is not yet completely cooled and has a consistency substantially: pasty. In addition, passing between the first 18 and second 19 outlet ducts, the aforementioned flow (which is a solid cylindrical body and pasty) takes a tubular shape, that is to say becomes a tube with a wall double layer.

  For example, the double layer structure of the wall 4 of the tube 1 before the latter undergoes the corrugation is shown, schematically, in Figure 6A. In particular, he. is noticed the main parcel 2 in PVC and the external wall arranged above 3 in polypropylene.

  It is observed that the PVC usually used to make the corrugated flexible tube does not have a high degree of purity. Indeed, the main wall 2 may comprise inside thereof impurities 30 in the form of grains which usually have microscopic dimensions. These microscopic grains or micrograins 30 are, for example, particles of soil or dirt which are deposited on the thermoplastic material.

  During the process of melting and homogenizing the PVC inside the main extruder 7, these micrograins amalgamate with the thermoplastic material by forming inclusions in the semi-fluid mass which is extruded.

  With reference to FIG. 6A, the micrograins 30 are represented by means of black spots with voluntarily exaggerated dimensions for the sake of simplicity of description.

  In the vicinity of the corrugation device 15, air is introduced or blown into the first outlet duct 18. In particular, the blown air is introduced through the other duct 21 connected to the outlet duct 18.

  This air blowing operation is known to those skilled in the field of flexible corrugated tubes.

  The blowing of air in the outlet duct 18 dilates the barely formed tube. As a result of this expansion, the wall 4, which is still very elastic in that it is not yet completely cooled and solidified, gradually adheres to the profiled shells 20 of the corrugation device 15 as shown in FIG. 6B.

  It is observed, moreover, that the profiled shells 20 rotate at the passage of the tube and cool progressively by conduction the wall 4 in his hand take, in the end, the characteristic wavy form shown in Figure 6C.

  In addition, as is deduced from FIGS. 6A, 6B and 6C, the outer wall 3 of the tube 1 is uniformly corrugated and simultaneously with the main wall 2 and therefore the use of two walls does not cause an excessive complication of the process. manufacturing.

  During the corrugation phase, the micrograins 30 present in the main wall 2 of PVC tend to move towards the outer wall 3 of polypropylene. As a result of this displacement, these micrograins 30 create, in correspondence of an interface 31 between the main wall 2 and the outer wall 3, vacuum zones which are no longer covered by the PVC. In other words, these vacuum zones correspond to real holes once the thermoplastic material has solidified.

  However, because of the immiscibility of PVC and polypropylene, micrograins of non-excessive dimensions have been observed to fail to pass through the outer wall 3. Thus, these micrograins remain trapped in the PVC wall and even the holes they cause develop at most in correspondence of the main wall 2.

  Advantageously, the outer wall 3 of polypropylene serves a protective function of the main wall 2, in that its immiscibility with the thermoplastic material of the main wall 2 causes the micrograin 30 to meet a discontinuity that prevents its passage to the wall external 3.

  In the case where it would be used for external parci 3 PVC or other thermoplastic material containing impurities during the corrugation phase .., these impurities could cause the formation of through holes in the outer wall. It is observed, however, that said holes only concern the outer wall 3 and not the inner one 2 because the expansion of the tube tends to move the impurities towards the outside of the tube.

  Advantageously, the outer wall 3 also represents an effective barrier against possible damage to the tube due to external causes. In particular, it is understood by external causes the mechanical abrasions that the flexible tube can undergo successively in the manufacturing phases. For example, such abrasions can occur as a result of tube conditioning operations (making of tube windings, arrangement on wooden pallets) or as a result of handling that the tube up to the phase of installation.

  It has been observed that the aforementioned abrasions concern at most the outer wall 3 of protection, they do not compromise the sealing characteristics of the tube 1.

  It has been noted that the corrugated tube 1 of the invention is substantially free of through-holes by ensuring adequate impermeability to the fluid-like construction materials that can be cast on it prior to laying electrical cables.

  In addition, the presence of the main walls 2 and outer 3 does not compromise the flexibility and the typical crush resistance of corrugated flexible tubes.

  Advantageously, the corrugated flexible tube 1 of the invention can be manufactured by slightly modifying the production devices used to manufacture a PVC single wall corrugated tube.

  Unlike traditional extrusion and corrugation equipment, the coextrusion head 11 has been modified by adding the plates of the cc-extrusion section 11a. However, with an apparatus having both plates, it is possible to manufacture the double-walled corrugated pipe or the single-wall PVC corrugated pipe by simply connecting or disconnecting the coextruder 8 with the common extrusion head 11, respectively.

  In addition, by simply varying the type and amount of extruded thermoplastic materials, it is possible to vary the properties of the corrugated flexible tube to be produced. For example, by introducing into the main extruder 7 hard PVC, there is obtained a corrugated flexible tube double wall more impact resistant.

  In another embodiment of the invention, the corrugated flexible tube 1 can be manufactured with the main wall 2 made of polypropylene and with the external wall 3 made of PVC by simply exchanging the thermoplastic materials that feed the main extruder 7 and the coextruder 8.

  It is observed that the tube of the invention can be manufactured by means of any combination of two thermoplastic materials provided that they are immiscible with each other.

  Advantageously, the main wall 2 can also be manufactured by using a recycled thermoplastic material (for example recycled PVC). Indeed, the nonuniformities of coloring of this material do not influence; on the aesthetic appearance of the tube because the coloration of the latter is determinable through the choice of the pigment used to color the outer wall 3 of coating.

  Of course, to the corrugated cable ducting tube and manufacturing method described in the present invention, the skilled person, in order to meet the contingent and specific requirements, may make other modifications and variants, all included by elsewhere within the scope of protection of the invention, as defined by the appended claims.

Claims (16)

  1. Corrugated flexible tube (1), preferably of cable-type type for electrical installations, comprising a corrugated main tubular wall (2) and made of thermoplastic material, characterized in that it further comprises an outer corrugated wall (3) which covers the main wall and having substantially matching corrugations with corresponding corrugations of the main wall, the outer wall being made of another thermoplastic material immiscible with that of the main wall.   2. corrugated tube (1) according to claim 1, wherein the thermoplastic material of the main tubular wall (2) is of such type that it may comprise grains (30) of impurities capable of generating holes in said wall during a production phase of the corrugated tube from said material.   3. Corrugated tube (1) according to claim 2, wherein the main wall (2) and the outer wall (3) define a separation barrier to prevent the migration of said grains (30) of the thermoplastic material to the other thermoplastic material substantially avoiding the formation of holes in the tube during said production phase of the corrugated tube.   4. Corrugated tube (1) according to claim 1, wherein the thermoplastic material of the main wall (2) is PVC or polypropylene and the thermoplastic material of the outer wall (3) is polypropylene or PCV, respectively .   The corrugated tube (1) according to claim 4, wherein said PVC and said polypropylene are immiscible at the respective extrusion temperatures.   The corrugated tube (1) according to claim 5, wherein said tube has an outer diameter of 20 mm and an inner diameter of 14 mm.   7. corrugated tube (1) according to claim 1, wherein the main wall (2) has a weight per meter greater than the weight per meter of the outer wall (3).   The corrugated tube (1) according to claim 1, wherein said thermoplastic materials and corrugations are capable of rendering said tube flexible and preventing its crushing from the outside.   9. Corrugated tube (1) according to claim 1 for receiving electrical cables and to be housed in interstices of walls, floors and the like, which can be brought into contact with construction materials in fluid form.   A method of manufacturing a corrugated flexible tube, comprising the steps of: - forming a corrugated main tubular wall (2) of said tube with a first thermoplastic material; forming an external corrugated tubular wall (3) of said tube with a second thermoplastic material for covering said main wall, the second material being immiscible with the first material.   11. The method of claim 10, comprising legs comprising: extruding the first material through a first opening (23) of an extrusion head (11) by obtaining a flow of said material to the semi-fluid state; extruding the second material through a second opening (24) of the extrusion head (11) to externally cover the flow of the first material.   The method of claim 11, further comprising the steps of: - imparting to the flow of the first material covered by the second material a tubular shape; - Waving the tubular flow of the first material covered by the second material so as to obtain said corrugated main wall (2) and outer wall (3).   13. The method of claim 12, wherein during the corrugation, it is possible to generate holes in said main wall (2) due to grains (30) of impurities included in the first material; said main wall and said outer wall (3) defining a separation barrier to prevent the migration of said grains (30) from the first material to the second thermoplastic material so as to prevent the formation of through holes in the tube during said waving step.   2867316 19 The method of claim 12, wherein the rippling step comprises the steps of: - passing said tubular stream through shaped shells (20) of a ripple device (15); - Expanding said tubular flow by blowing to adhere to the profiled shells of the corrugator.   15. The method of claim 14, comprising a step of cooling the corrugated tubular flow so as to obtain the corrugated tube.   16. Apparatus (100) usable for the method of manufacturing a corrugated flexible tube (1) according to at least one of claims 10 to 15, the apparatus comprising.   a main extruder (7) for extruding a first thermoplastic material; a co-extruder (8) for extruding a second thermoplastic material; an extrusion head (11) connected to the main extruder and the co-extruder, provided with a first opening (23) for a flow of the first extruded material in the semi-fluid state and a second opening (24) for a flow of the second material as it covers the outside. the flow of the first material; said extrusion head being such as to cause the flow of the second material to be distributed over the first material, avoiding the formation of a mixture of said materials; a pair of coaxial tubular outlet ducts (18, 19) connected to the extrusion head (11) to give the flt: x of the first material covered by the second material a substantially tubular shape by obtaining a tube with a double layer (4); - a ripple device (15) operatively associated with said output conduits and including shaped shells (20) for waving the double layer tube; another tubular duct (21) for introducing a blowing fluid into said double-walled tube so as to extend it to adhere to said profiled shells and to produce corrugations in the double-layered wall .